Synthesis, anti-HIV activity studies, and in silico rationalization of cyclobutane-fused nucleosides

The present work describes some recent approaches to novel 3-oxabicyclo[3.2.0]heptane-type nucleosides structurally similar to the potent anti-HIV agent stavudine (d4T). To gain knowledge at the molecular level relevant for further synthetic designs, the lack of activity of these compounds was investigated by computational approaches accounting for three main physiological requirements of anti-HIV nucleosides: their drug-likeness, their activation process, and their subsequent interaction with HIV reverse transcriptase (HIV-RT). Our results show that the inclusion of the fused cyclobutane at the 2'- and 3'-positions of the sugar portion provides drug-like compounds. Nonetheless, the presence of this cyclobutane moiety prevents binding orientations consistent with the catalytic activation for at least one of the enzymes known to activate d4T. To the best of our knowledge, this is the first study to explicitly consider the simulation of the entire activation process to rationalize anti-HIV activities.